Obama aide in geo-engineering row

President Obama's science adviser got into a spat with the media last week after appearing to advocate geo-engineering as a way to mitigate the effects of global warming.

John Holdren, who became the president's adviser for science and technology in December, was quoted in an interview with the Associated Press suggesting that climate change has become so severe that drastic moves may be required.

Geo-engineering involves large engineering projects on a global scale as a means of changing the planet's climate. Examples that have been proposed include dropping sulphur in the upper reaches of the atmosphere to stop some of the sun's heat reaching the earth's surface.

"We're talking about all these issues in the White House," Holdren was quoted as saying by the AP in a discussion about geo-engineering. "There's a very vigorous process going on of discussing all the options for addressing the energy climate challenge."

Holdren reacted negatively to the AP's headline and the emphasis in the interview, suggesting that the geo-engineering angle had been overplayed.

In a subsequent interview with the New York Times, Holdren attempted to correct matters. "I said the approaches that have been surfaced so far seem problematic in terms of both efficacy and side effects, but we have to look at the possibilities and understand them because if we get desperate enough it will be considered. I also made clear that this was my personal view, not administration policy."

Holdren did confirm that geo-engineering has been the subject of White House discussions. "This is not the same thing as saying the White House is giving serious consideration to geo-engineering - which it isn’t - and I am disappointed that the headline and the text of the article suggest otherwise," he told the NYT.

Some outlandish geo-engineering schemes have been suggested by scientists, including painting vast swathes of the earth's surface white to reflect sunlight, or launching amadas of mirrors into orbit to shield the planet from a proportion of the sun's rays.